Auto-relieving pressure modulating valve

ABSTRACT

An auto-relieving pressure modulating valve includes a spool, a solenoid that shifts the spool in an energized direction, and a spring arrangement. The spring arrangement functions to shift the spool from a relieving position to a neutral position, in the energized direction, without energizing the solenoid.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional of application Ser. No.09/976,383, filed Oct. 11, 2001; which application is incorporatedherein by reference.

FIELD OF THE INVENTION

[0002] This disclosure concerns a solenoid valve assembly. Morespecifically, this disclosure describes a solenoid actuated brake oractuator assembly.

BACKGROUND OF THE INVENTION

[0003] A wide variety of electrohydraulic pressure reducing andrelieving valves are used to provide controlled pressure to hydraulicactuators and brake cylinders, for example. Some typical valves aredesigned for use with a proportional electric solenoid, which generatesa thrust force proportional to the electrical current fed to thesolenoid. The size and cost of the proportional solenoid are a functionof the force output and the stroke over which this force output isavailable. Thrust force of proportional solenoid valves is proportionalonly within a predetermined stroke length. For a given size and cost,the predetermined proportional stroke length may be exceeded, but onlywith reduced force. Thus, to maximize the force capability of aproportional solenoid valve, it is desirable to maintain the strokelength within the proportional range. Typical proportional solenoidvalves have moving armatures that travel farther than the proportionalstroke range. Farther travel in the valve is desirable to provide forquicker activation or release of a working unit by increasing the flowrate through the valve body. Moving the armature as far over as possiblein an activation or release position increases the flow rate. Theproblem is that as the stroke of the armature exceeds the proportionalrange, the thrust force rapidly decreases. Therefore, current designsare limited in providing adequate flow rate due to the constraint of therelationship between stroke length and force output.

[0004] In general, improvement has been sought with respect to suchvalve arrangements, generally to better accommodate increasing overallvalve spool and armature travel while maintaining proportional strokelength to maximize force output.

SUMMARY OF THE INVENTION

[0005] One aspect of the present invention relates to a solenoid valveassembly having an auto-relieving valve arrangement that utilizes themaximum stroke length and force output of a proportional solenoid valvewhile providing added stroke travel to increase flow rate capacitywithout exceeding the solenoid's proportional range.

[0006] Another aspect of the present invention relates to a valvearrangement having a biasing component that biases a spool in anenergized direction, from a relieving position to a neutral position,without energizing a solenoid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate embodiments ofprinciples of this disclosure and, together with the description, serveto explain these principles.

[0008]FIG. 1 is a cross-sectional view of one embodiment anauto-relieving valve arrangement shown in a neutral position accordingto the principles of this disclosure.

[0009]FIG. 2 is a cross-sectional view of the auto-relieving valvearrangement of FIG. 1, shown in an energized position.

[0010]FIG. 3 is a cross-sectional view of the auto-relieving valvearrangement of FIG. 1, shown in a relieving position.

[0011]FIG. 4 is a cross-sectional view of a spool taken along line 4-4shown in FIG. 1.

[0012]FIG. 5 is a cross-sectional view of the spool taken along line 5-5shown in FIG. 1.

[0013]FIG. 6 is a cross-sectional view of another embodiment of anauto-relieving valve arrangement shown in a neutral position accordingto the principles of this disclosure.

[0014]FIG. 7 is a cross-sectional view of the auto-relieving valvearrangement of FIG. 6, shown in an energized position.

[0015]FIG. 8 is a cross-sectional view of the auto-relieving valvearrangement of FIG. 6, shown in relieving position.

[0016]FIG. 9 is a side view of the washer shown in FIG. 6.

[0017]FIG. 10 is a front view of the washer of FIG. 9.

DETAILED DESCRIPTION

[0018] With reference now to the various drawing figures in whichidentical elements are numbered identically throughout, a description ofvarious exemplary aspects of the present invention will now be provided.

[0019]FIG. 1 illustrates, in cross-section, one embodiment of a valveassembly 10 according to the principles of this disclosure. In general,the valve assembly 10 includes a valve body 26 coupled to a solenoidassembly 28. Typically, the valve assembly 10 is used in conjunctionwith a hydraulic pressure unit or hydraulic pump 12, a hydraulicreservoir or tank 14, and a working unit 16 such as, for example, ahydraulic cylinder or brake.

[0020] For purposes of clarification, the valve assembly 10 will bedescribed as having a first end 36 and a second end 38. Also, the valveassembly 10 will be described as having components moving in anenergized direction 36′ and a de-energized direction 38′. The energizeddirection 36′ is opposite the de-energized direction 38′.

[0021] The valve body 26 of the valve assembly 10 includes a bore 24, apressure port 18, a work port 20, and a tank port 22. The bore 24typically extends through the valve body 26. Each of the ports 18, 20and 22 are in fluid communication with the bore 24. In the illustratedembodiment, the pressure port 18 is disposed proximate the first end 36and the tank port is disposed proximate the second end 38. The work port20 is disposed intermediate the pressure and tank ports 18, 22. As shownschematically in FIG. 1, the ports 18, 20, and 22 provide connectionlocations for establishing fluid communication between the valve body 26and the hydraulic pump 12, the working unit 16, and the tank 14. Typicalport connections include standard SAE straight threads or otherconfigurations for allowing hoses or other conduits to be connectedbetween the components.

[0022] Alternative embodiments having other port configurations arecontemplated, for example, the pressure port 18 may be disposedproximate the second end 38 and the tank port 22 may be disposedproximate the first end 36. A second embodiment, which discloses anotheralternative configuration, is described in detail below.

[0023] The bore 24 includes a first annular surface 30 and a secondannular surface 32. These surfaces cooperate with the solenoid assemblyto direct fluid communication between the ports 18, 20, and 22 as thesolenoid assembly is energized and de-energized. The bore 24 alsoincludes a countersink region 34. In the illustrated embodiment, thecounter sink region 34 is proximate the second end 38.

[0024] The bore 24 is configured to receive a spool 42 of the solenoidassembly 28. The solenoid assembly 28 generally includes an armature(not shown), such as a common coil and iron core armature. The spool 42is coupled to the armature so that when the solenoid assembly 28 isenergized, the spool 42 moves in accordance with the armature from ade-energized neutral position to an energized position. The neutralposition and the energized position of the spool 42 are shown in FIGS. 1and 2 respectively. In the illustrated neutral position of FIG. 1, fluidcommunication is provided between the work port 20 and the tank port 22.The energized position (shown in FIG. 2), provides fluid communication(as shown by the arrow) between the pressure port 18 and the work port20. It is to be understood that the solenoid may operate in thealternative where, for example, the energized position provides fluidcommunication between a work port and a tank port and the neutralposition provides fluid communication between a pressure port and thework port.

[0025] The spool 42 includes a first annular portion 44 and a secondannular portion 46. The annular portions 44 and 46 are configured tocoincide with the first and second annular surfaces 30 and 32 of thebore 24. The spool 42 also comprises a shoulder 48 proximate the secondend 38 of the valve assembly 10.

[0026] In the illustrated embodiment, the valve assembly 10 includes aspring 50 and a spring retaining member 54. The retaining member 54 maybe an extended portion of the solenoid assembly 28 or a separate valveassembly component. The spring 50 is positioned within the countersinkregion 34 of the bore 24. The spring 50 may comprise a variety ofcompression spring configurations. Other spring types that may be usedinclude bevel springs, torsion springs with levers, leaf springs, andthe like.

[0027] The spring retaining member 54 is configured with an interiorshoulder 56. The spring 50 is positioned longitudinally between theshoulder 48 of the spool 42 and the interior shoulder 56 of theretaining member 54. The retaining member 54 functions as a stationarycomponent against which the spring 50 is compressed. In the illustratedembodiment, the spool 42 includes an extended portion 58 having aninside diameter sized to guide the spring 50. The extended portion 58maintains the spring 50 in a longitudinal orientation.

[0028] In the illustrated embodiment, a washer 60 is disposed betweenthe shoulder 48 of the spool and the spring 50. The washer 60 provides amechanical stop to the spring compression. Additionally, the washer 60functions to define the neutral position of the spool 42. As shown inFIG. 1, the washer 60 contacts the bottom of the countersink region 34due to tension from spring 50 acting directly on the washer 60. Thewasher 60 also contacts the shoulder 48 of spool 42 due the tension fromspring 70 acting on the spool 42. The tension from spring 70 is somewhatless than the tension provided by spring 50 when the valve arrangement10 is in the neutral position. The washer 60 therein defines the neutralposition of the valve assembly 10 such that the starting position forthe proportional stroke of the solenoid assembly 28 is uniform inmanufacture, regardless of minor variations in the tension provided bysprings 70 and 50. Likewise, the washer 60 defines a neutral positiongap 64 between the work port and tank port, which will be discussed indetail below.

[0029] It is to be understood that spring compression may be adapted tovarious applications by modifying the length of the spring retainingmember, the thickness of the washer, the stiffness of the spring, orother various structural features as would be obvious to one of ordinaryskill in the art.

[0030] In the illustrated embodiment, the bore 24 is manufactured as athrough bore extending through the valve body 26. It is contemplatedthat the bore 24 may also be configured as a blind bore. A threaded capor plug 72 is positioned proximate the first end 36 within the bore 24of the valve assembly 10. The plug 72 functions as a stationarycomponent in operation with a dowel 40 and the relative movement of thespool 42.

[0031] The spool 42 is operatively arranged with the dowel 40 so as toslide relative to the dowel 40. The presence of the dowel 40 causes afirst surface area 100 of the spool, (shown in FIG. 4) to be less thanan opposing surface area 102 of the spool 42 (shown in FIG. 5). Thesesurface areas 100 and 102 create an unbalanced pressure load on thespool 42 when the valve body is pressurized. This unbalanced pressureload biases the spool 42 in the de-energized direction 38′.

[0032] Typically, the valve assembly 10 includes a feedback component orreturn spring 70. In the illustrated embodiment, the return spring 70 isretained by the plug 72 and biases the spool 42 in the de-energizeddirection 38′. The spring 70 acts to return the spool 42, relative tothe dowel 40, to the neutral position (shown in FIG. 1) when thesolenoid valve 28 is de-energized. The spring may comprise any standardspring commonly used and known by those having skill in the art or anyother feed-back device such as pneumatic struts, electromagnets, orelastomeric force feed-back devices. Alternatively, the return spring 70may be omitted in applications where the unbalanced work port pressurealone is used to return the spool to the neutral position. The remainderof this disclosure will discuss operation of this embodiment includingthe return spring 70. It is to be understood that an embodiment omittingthe return spring operates in similar fashion in accordance with theprinciples disclosed.

[0033] In use, when pressurized fluid is desired to operate the workingunit 16, the solenoid valve 28 is energized. The solenoid beginsdeveloping axial force from the neutral position shown in FIG. 1. Thesolenoid valve 28 shifts or moves the spool 42 in the energizeddirection 36′ to the energized position shown in FIG. 2. In theenergized position, pressurized fluid is permitted to flow from thepressure port 18 around a flow portion 68 of the spool 42 having adecreased diameter and to the work port 20 for operation of the workingunit 16. At the same time, fluid flow to the tank port 22 is obstructedby a close fit between the second annular surface 32 of the valve body26 and the second annular portion 46 of the spool 42.

[0034] The pressurized fluid acts on the imbalanced surface areas 100and 102 of the spool 42. As the pressure increases, the pressure forceapproaches the solenoid force and the spool 42 begins to move in thede-energized direction 38′. Spool movement in the de-energized direction38′ increases fluid communication with the tank port 22 and decreasesfluid communication with the pressure port 18, thereby causing pressureat the work port 20 to stabilize or drop. With pressure drop, net forcein the energized direction 36′ exceeds net force in the de-energizeddirection 38′ causing movement in the energized direction 36′. Spoolmovement in the energized direction 36′ decreased fluid communicationwith the tank port 22 and increases fluid communication with thepressure port 18. This process or cycle causes “modulation” (i.e. backand forth movement) of spool 42. During modulation, the solenoid remainsenergized. The spool modulates until the pressure force and spring force70 is balanced against the solenoid force. At steady state equilibrium,(when the kinematic energy forces resulting from a changes in solenoidcurrent or brake pressure have subsided) the spool 42 will attain astabilized position where fluid flow from the pressure port to the workport equals the fluid flow from the work port to the tank port.

[0035] Upon desired release of the pressurized fluid, the solenoid valve28 is de-energized and no longer produces solenoid force in theenergized direction 36′. The spool 42 moves in the de-energizeddirection 38′ by the imbalance of pressure force and the force from thereturn spring 70. At the neutral position there is still significantresidual work port pressure, as the spool 42 has not traveled far enoughto accommodate sufficient relieving fluid flow. The combination of thereturn spring force, and the force resulting from the residual work portpressure compresses the opposing spring 50 to allow the spool 42 to movebeyond the neutral position to the relieving position (as shown in FIG.3). In the relieving position, pressurized fluid is permitted to rapidlyflow from the work port 20 around the flow portion 68 of the spool 42and to the tank port 22.

[0036] As the fluid is released, the fluid pressure force acting tocompress spring 50 decreases. The spring 50 eventually overcomes thecombined forces and shifts the spool 42 forward to the neutral positionshown in FIG. 1. In this position, the necessary fluid flow need onlyaccommodate leakage from the pressure port 18 into the bore 24 toprevent unwanted pressure buildup from actuating the working unit 16.The washer 60 contacting the bottom surface of the countersink area 34determines the neutral position of the spool.

[0037] Referring back to the energized position of FIG. 2, fluidcommunication is provided from the pressure port 18 through a pressureport gap 62 between the first annular portion 44 of the spool 42 and theannular surface 30 of the valve body 26. Likewise, as shown in FIG. 1,when the spool 42 is in the de-energized, neutral position, fluidcommunication is provided to the tank port 22 through a neutral gap 64.Further, referring now to FIG. 3, the spool 42 is shown in a fullexhaust or relieving position wherein a relieving gap 66 provides forfluid communication from the work port 20 to the tank port 22. Therelieving gap 66 has a cross-sectional area that is greater than theneutral gap 64. The neutral gap 64 need only accommodate a minimal flowrate to prevent unwanted build up of pressure in a brake line of aworking unit 16, for example. The relieving gap 66 is greater than theneutral gap 64 to accommodate a greater flow rate for rapid release ofthe working unit 16.

[0038] The cross-sectional area of the full relieving gap 66 may beseveral times greater in cross-sectional area than the neutral gap 64.In the illustrated embodiment, the cross-sectional area of the relievinggap 66 is about 1.5 to 3.5 times greater. It is contemplated that inlarger applications, the ratio between the relieving gap and the neutralgap can be up to 20 times greater. Accordingly, the flow rate throughthe relieving gap 66 is likewise greater than the flow rate through theneutral gap 64.

[0039] The required flow rate from the work port 20 to the tank port 22is determined by the amount of flow required in the application, forexample, the amount of flow necessary to disengage a hydraulic actuatoror hydraulic brake within an acceptable amount of time. For a givenspool configuration, the open area or gap providing for fluidcommunication between ports is a function of spool stroke or spooltravel. Greater flow rates require greater cross-sectional flow areas orgaps and therein require the spool to travel farther to increase thearea of the gap. Similarly, when the solenoid is first energized therequired flow rate from the pressure port 18 to the work port 20 isdetermined by the amount of flow required in the application, forexample, the amount of flow necessary to actuate a hydraulic brakewithin an acceptable amount of time.

[0040] In conventional designs, the required flow rate from work port totank port defined and fixed the neutral position; and the stroke equaledthe sum of the travel required to accommodate the needed flow rate fromthe pressure port, any small overlap required to minimize leakage, plusthe travel required to accommodate the needed flow rate to the tankport. In other words, the neutral position in conventional designs istraditionally also the fully released position.

[0041] In accordance with the principles disclosed, the stroke of theillustrated embodiments need only include the travel necessary toaccommodate the pressure port flow rate, any small overlap required tominimize leakage, plus a minor opening sufficient to handle steady stateor equilibrium leakage from the work port to tank port. The proportionalstroke length of the valve assembly 10 is not limited or depleted byhaving to account for travel to accommodate the required flow rate tothe tank port. Therein, the valve assembly 10 provides increased flowrate capacity for a given spool size, or proportional solenoid strokelength, not attainable by traditional arrangements. In the alternative,the valve assembly 10 may incorporate a smaller solenoid assembly tominimize cost or size of the valve assembly for a particular given flowrate capacity.

[0042] To further explain, when the solenoid 28 is switched from anenergized state to a de-energized state, the pressurized fluid from thework port 20 works in combination with the return spring 70 to bias thespool 42 in the de-energized direction 38′. Upon solenoidde-energization, the immediate work port fluid pressure is greatest. Thecombined pressure force and return spring 70 force move the spool 42 tothe relieving position shown in FIG. 3, and at the same time compressthe spring 50 in the de-energizing direction 38′. The relieving gap 66,which exhausts the pressurized fluid, is maximized to provide quickrelease or engagement of the working unit.

[0043] When the work port pressure begins to equalize with the tank portpressure, the spring 50 returns the spool to the neutral position in theenergized direction 36′, without assistance from the solenoid. In otherwords, the spool 42 travels from a first de-energized position to asecond de-energized position. This configuration and arrangement inessence shifts the neutral position of the valve assembly 10 forwardfrom the first de-energized position to the second de-energizedposition. By shifting the neutral position forward, maximum strokelength and thrust force are available to shift the spool 42 to anenergized position having greater flow capacity.

[0044] In typical prior art configurations, a fixed stroke lengthdetermined the valve's flow rate capabilities, i.e., a user requiringquicker exhausting capability would have to sacrifice input capability.In the present invention, the exhausting capability is maximized withoutsacrificing input capability by action of the spring 50 shifting theneutral position forward. In other words, the arrangement providesgreater actual stroke length without jeopardizing proportional traveland maximum thrust force.

[0045]FIG. 6 depicts, in cross-section, a second embodiment of a valveassembly 110 according to the principles of this disclosure. In general,the valve assembly 110 includes a valve body 126 coupled to a solenoidassembly 128. The valve body 126 of the valve assembly 110 includes abore 124, a pressure port 118, a work port 120, and a tank port 122. Inthis port configuration, the tank port 122 extends from the bore 124;however, the overall principles of operation of this secondconfiguration are similar to those disclosed in the first embodiment.

[0046] When the spool 142 is in the de-energized neutral position (shownin FIG. 6), fluid communication is provided from the work port 120 tothe tank port 122 through a neutral gap 164. A cross-shaped washer orcomponent 174 accommodates fluid communication to the tank port 122 inthis embodiment. As best shown in FIGS. 9 and 10, the cross-shapedcomponent 174 includes recessed portions 176 through which fluid flows.The cross-shaped component 174 functions to provide a stationary centersurface 178 against which the dowel 140 may act. This permits unbalancedpressure forces to bias the spool 142 in the de-energized direction 182′relative to the dowel 140, as discussed previously.

[0047] In accordance with the principles disclosed, FIG. 7 illustratesthe valve assembly 110 in an energized position. Fluid communication isprovided from the pressure port 118 through a pressure port gap 162 andaround a flow portion 168 of the spool 142, to the work port 120.

[0048] Upon desired release of the pressurized fluid, the solenoid valve128 is de-energized. Return spring 170 and the imbalance of pressureforces move the spool 142 to a relieving position shown in FIG. 8. Thecombination of the return spring force, and the force resulting from theresidual work port pressure compresses opposing spring 150 to allow thespool 142 to move beyond the neutral position to the relieving position.(As discussed previously, the return spring 170 may be omitted.) In therelieving position, the relieving gap 166 provides a greatercross-sectional area than the neutral gap 164 for rapid fluid flow fromthe work port 120 to the tank port 122. As fluid is exhausted, the fluidpressure force acting to compress spring 150 decreases. The spring 150eventually overcomes the combined forces and shifts the spool 142 in theenergized direction 180′ to the neutral position (shown in FIG. 6),without having to energize the solenoid 128. Overall, this secondembodiment provides all the advantages in accordance with the principlesdisclosed by the first embodiment. Additionally, the second embodimentis beneficial by reducing manufacturing operations. Specifically, oneport, i.e. the tank port 122, is configured as an extension of the valvebody bore 124 and therein eliminates machining a separate tank port.

[0049] The above specification and examples provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the principles disclosed, theinvention resides in the claims hereinafter appended.

I claim:
 1. A method of controlling fluid flow in a valve arrangement,the valve arrangement including a valve body having a pressure port, awork port, and a tank port, a solenoid device coupled to the valve body,and a spool operably coupled to the solenoid device, the methodcomprising: (a) pressurizing the work port by energizing the solenoiddevice and moving the spool a first distance from a neutral position toa pressurized position; (b) relieving the work port by de-energizing thesolenoid device and moving the spool a second distance to a relievingposition, the second distance being greater than the first distance, thevalve arrangement being configured to provide a first gap for fluidcommunication between the work port and the tank port when the spool isin the relieving position, the first gap of the valve arrangement havinga first cross-sectional area; and (c) moving the spool, withoutenergizing the solenoid device, from the relieving position to theneutral position, the valve arrangement being configured to provide asecond gap for fluid communication between the work port and the tankport when the spool is in the neutral position, the second gap of thevalve arrangement having a second cross-sectional area, the firstcross-sectional area of the first gap being greater than the secondcross-sectional area of the second gap.
 2. The method of claim 1,wherein the first cross-sectional area of the first gap is up to 20times greater than the second cross-sectional area of the second gap. 3.The method of claim 1, wherein the first cross-sectional area of thefirst gap is about 1.5 to 3.5 times greater than the secondcross-sectional area of the second gap.
 4. The method of claim 1,wherein the second cross-sectional area of the second gap is sized andconfigured to accommodate leakage from the pressure port into the valvearrangement to prevent unwanted pressure buildup within the work port.5. The method of claim 1, wherein the valve arrangement includes onlyone solenoid valve.